1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display capable of improving a color reproduction range.
2. Discussion of the Related Art
Generally, flat plate displays include a liquid crystal display, a field emission display, a plasma display panel, a light emitting device and the like.
The liquid crystal display displays an image by adjusting a light transmittance of liquid crystal using an electric field. For this, an image display device includes a display panel having liquid crystal cells, a back light unit which illuminates light on the display panel and a driving circuit for driving the liquid crystal cells.
The display panel is formed to define a plurality of unit pixel regions by crossing a plurality of gate lines and a plurality of data lines. In each pixel region, there are provided a thin film transistor array substrate and a color filter array substrate facing each other, spacers positioned between two substrates to maintain a specific cell gap, and liquid crystal filled in the cell gap.
The thin film transistor array substrate includes gate lines and data lines, thin film transistors formed as switch devices at crossing portions of the gate lines and the data lines, pixel electrodes connected to the thin film transistors in respective liquid crystal cells, and an orientation film coated thereon. The gate lines and data lines are supplied with signals from driving circuits through respective pads.
The thin film transistors supply pixel voltage signals, which are supplied to the data lines, to the pixel electrodes in response to scan signals supplied to the gate lines.
The color filter array substrate includes color filters formed in the respective liquid crystal cells, black matrices for distinguishing the color filters from each other and reflecting outside light, common electrodes which commonly supply reference voltages to the liquid crystal cells, and an orientation film coated thereon.
After the separately manufactured thin film transistor array substrate and color filter array substrate are arranged, the substrates are bonded to face each other. Then, the liquid crystal is injected therein and sealed, thereby accomplishing the liquid crystal display.
A method for reproducing colors in the liquid crystal display device employs a pixel structure in which a color filter region corresponding to the red (R), green (G) and blue (B) of three primary colors of light is defined as one dot, transmittance of white light is adjusted while passing through a liquid crystal layer, and light passes through individual red (R), green (G) and blue (B) pixels, thereby representing various colors. The individual red (R), green (G) and blue (B) pixels can represent various colors by combination of RGB.
FIG. 1 illustrates RGB individual pixels in a unit pixel having a sensor among 4×4 pixels in a conventional liquid crystal display.
As shown in FIG. 1, in a case of a 7″ WVGA liquid crystal display, a unit pixel has a dot pitch of 190.5 μm, and the individual red (R), green (G) and blue (B) pixels forming the unit pixel have a dot pitch of 63.5 μm. In this case, as for the size of pixel electrodes in the individual red (R), green (G) and blue (B) pixels, the pixel electrode in a pixel without a sensor has an area A, whereas the pixel electrode in a pixel having a sensor has an area B. Accordingly, it causes a difference in an opening ratio of the individual pixels.
As a result of measuring a color reproduction range in unit pixel regions having a difference in an opening ratio, a unit pixel without a sensor represents normal brightness (color), i.e., R (255 grey)+G (255 grey)+B (255 grey)=W (255 grey), whereas a unit pixel having a sensor cannot represent a desired color, i.e., R (255 grey)+G (255 grey)+B (250 grey)=Yellowish White (less than 255 grey).
Accordingly, in the individual pixels having the same dot pitch, since color mixture is not properly made due to a difference in an opening ratio of the unit pixel without a sensor and the unit pixel having a sensor, it is difficult to accurately represent colors. Thus, there is a problem of deteriorating image quality in the liquid crystal display.
Further, in a case where one or more individual pixels include a sensor in the liquid crystal display having a sensor, the reduction of image quality becomes severer.